Deering makes the finest 17-fret and 19-fret tenor banjos today. Tenor banjos are 4 string banjos that are traditionally tuned in 5ths (C,G,D,A - standard tuning, G,D,A,E - Irish tuning). These types of banjos are traditionally used for either Traditional New Orleans Jazz or Irish music.
Jazz players most often use a 19 fret tenor banjo because it gives the banjo a larger range. Irish players vary between using the 17 fret tenor or the 19 fret tenor. The 17 fret has a smaller scale so the frets are closer together, making it easier to play quick single note passages - something that is often done in Irish music.
Both banjos can also be tuned to Chicago tuning which is the top 4 strings of a guitar (D,G,B,E). Learn how to choose the correct strings for this tuning here.